J/A+A/645/A95 NEP raster ROSAT X-ray/Optical catalog (Hasinger+, 2021)
The ROSAT raster survey in the north-ecliptic pole field:
X-ray catalogue and optical identifications.
Hasinger G., Freyberg M., Hu E.M., Waters C.Z., Capak P., Moneti A.,
McCracken H.J.
<Astron. Astrophys. 645, A95 (2021)>
=2021A&A...645A..95H 2021A&A...645A..95H (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; X-ray sources ; Active gal. nuclei ; Clusters, galaxy ;
Infrared sources ; Optical
Keywords: surveys - catalogs - galaxies: nuclei - quasars: general -
X-rays: galaxies - X-rays: galaxies: clusters
Abstract:
The North-Ecliptic Pole is an important region for extragalactic
surveys. Deep/wide contiguous surveys are being performed by several
space observatories. We analyse all ROSAT pointed and survey
observations within 40deg2 around the NEP, restricting the
field-of-view to the inner 30' radius. We obtain an X-ray catalogue of
805 sources with 0.5-2keV fluxes >2.9*10-15erg/cm2/s, a factor of
three deeper than the ROSAT All-Sky Survey in this field. The
sensitivity and angular resolution of our data are comparable to the
eROSITA All-Sky Survey expectations. The 50% position error radius of
the sample of X-ray sources is ∼10". We use HEROES optical and
near-infrared imaging photometry from Subaru and CFHT telescopes
together with literature catalogues and a new deep and wide Spitzer
survey in the field to identify X-ray sources and calculate
photometric redshifts for the candidate counterparts. In particular we
utilize mid-IR colours to identify AGN X-ray counterparts. Despite
relatively large error circles and faint counterparts, confusion and
systematic errors, we obtain a rather reliable catalogue of 766
optical counterparts, redshifts and optical classifications. We find a
new population of luminous absorbed X-ray AGN at large redshifts, not
recognized in previous X-ray surveys, but identified in our work due
to the unique combination of survey solid angle, X-ray sensitivity and
multiwavelength photometry. We also use the WISE and Spitzer
photometry to identify a sample of 185 AGN selected purely through
mid-IR colours, most of which are not detected by ROSAT.
Their redshifts and upper limits to X-ray luminosity and
X-ray-to-optical flux ratios are even higher than for the new
class of X-ray selected luminous type 2 AGN (AGN2); they are probably
a natural extension of this sample. This unique dataset is important
as a reference sample for future deep surveys in the NEP region, in
particular for eROSITA and also for Euclid and SPHEREX. We predict
that most of the absorbed distant AGN should be readily picked up by
eROSITA, but they require sensitive mid-IR imaging to be recognized as
optical counterparts.
Description:
805 X-ray sources detected in the ROSAT NEP Raster Scan survey, as
well as their optical/IRcounterparts based on deep optical/IR
photometry from the Subaru and CFHT telescopes, as well as the Spitzer
Space Observatory. In the same field a selection of 185 AGN candidates
has been selected purely based on mid-IR colours.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 73 805 ROSAT NEP raster X-ray catalogue
table3.dat 119 920 ROSAT NEP candidate optical ID catalogue
table4.dat 85 185 AGN candidates selected by mid-IR colours
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See also:
J/ApJ/617/192 : ROSAT AGN Catalog in North Ecliptic Pole (Mullis+, 2004)
J/ApJS/162/304 : ROSAT NEP X-ray source catalog (Henry+, 2006)
J/A+A/461/977 : Rosat North Ecliptic survey stellar population (Micela+, 2007)
J/A+A/588/A103 : Second ROSAT all-sky survey (2RXS) source catalog
(Boller+, 2016)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- XID [1/805] Internal X-ray identification number
5- 15 F11.7 deg RAXdeg X-ray right ascension (J2000.0)
17- 26 F10.7 deg DEXdeg X-ray declination (J2000.0)
28- 31 F4.1 arcsec ePosX X-ray position error
33- 39 F7.1 --- ML Existence maximum likelihood (threshold 11)
41- 46 F6.1 ct CTS Net X-ray source counts
48- 51 F4.1 ct e_CTS Error on net source counts
53- 57 F5.1 --- XML Extent maximum likelihood
59- 64 I6 s ExpTime Exposure time
66- 71 F6.2 10-17W/m2 FX 0.5-2 keV X-ray flux (1)
73 I1 --- FlagM [0/1] Manual parameter determination flag
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Note (1): in units of 10-14erg/cm2/s.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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2- 4 I3 --- XID Internal X-ray identification number
5 A1 --- m_XID [abcd] letters for multiple counterparts
7- 17 F11.7 deg RAOdeg Optical counterpart right ascension (J2000.0)
19- 29 F11.8 deg DEOdeg Optical counterpart declination (J2000.0)
31- 34 F4.1 mag magOpt Optical AB magnitude in r_mag Band
36 A1 --- r_magOpt [GPSirz] Source of the optical
magnitude/coordinates (1)
38- 42 F5.2 --- FX/FO X-ray to optical flux ratio
44- 47 F4.1 mag magIR ? Infrared AB magnitude in r_magIR band
49 A1 --- r_magIR [Wi] Source of the infrared magnitude (2)
51- 55 F5.2 --- CI1-2 ? Mid-infrared colour WISE W1-W2 or IRAC I1-I2
57 I1 --- Class Optical counterpart ID class (3)
59- 63 F5.3 --- z ? Redshift
65- 68 A4 --- Q Quality of redshift (4)
70- 73 F4.1 [10-7W] logLX ? log (0.5-2keV luminosity), in erg/s unit
75 I1 --- IDQ [0/2] Identification quality (5)
77-119 A43 --- Com Notes on individual objects
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Note (1): Source of the optical magnitude/coordinates flags as follows:
G = Gaia
P = Pan-STARRS
S = SDSS
i = HSC i
r = HSC r
z = HSC z
Note (2): Source of the infrared magnitude flag as follows:
W = CatWISE2020 W1
i = IRAC I1
Note (3): Optical counterpart ID class code as follows:
1 = AGN1
2 = AGN2
3 = Galaxy
4 = cluster/group
5 = star
Note (4): Quality of redshift flag as follows:
ph = photometric
NED = literature
Keck = DEIMOS
KCWI = new spectroscopic z
WIYN = new spectroscopic z
Note (5): Identification quality flag as follows:
2 = high quality identification
1 = ambiguous
0 = rejected
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 11 F11.7 deg RAIdeg Mid-IR AGN candidate right ascension (J2000.0)
13- 23 F11.8 deg DEIdeg Mid-IR AGN candidate declination (J2000.0)
25- 28 F4.1 mag magOpt Optical AB Magnitude
30- 33 F4.1 mag I1mag IRAC I1 AB magnitude
35- 38 F4.2 mag I1-I2 Mid-infrared colour IRAC I1-I2
40- 43 F4.2 mag e_I1-I2 Error of mid-IR colour
45 I1 --- Class [1/2] Mid-IR AGN candidate ID class (1)
47- 50 F4.2 --- zph Photometric redshift
52- 56 F5.1 --- ML Existence maximum likelihood
58- 62 F5.2 ct uCTS Net X-ray source count upper limit
64- 69 I6 s ExpTime Exposure time
71- 74 F4.2 10-17W/m2 uFX Upper limit to 0.5-2 keV X-ray flux (2)
76- 80 F5.2 --- uFX/FO Upper limit to X-ray to optical flux ratio
82- 85 F4.1 [10-7W] ulogLX Upper limit log (0.5-2 keV luminosity)
in erg/s unit
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Note (1): mid-IR AGN candidate ID class code as follows:
1 = AGN1
2 = AGN2
Note (2): in units of 10-14erg/cm2/s.
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Acknowledgements:
Guenther Hasinger, ghasinger54(at)gmail.com
(End) Guenther Hasinger [ESA], Patricia Vannier [CDS] 16-Nov-2020